1. Field of the Invention
The present invention relates to soft magnetic films for use as, for example, magnetic layers in thin film magnetic heads, and magnetic cores in inductors or the like, and more particularly, to soft magnetic films in which a magnetostriction constant can be reduced while maintaining soft magnetic properties and to thin film magnetic heads, planar magnetic elements (e.g., transformers and inductors), and filters using the soft magnetic films.
2. Description of the Related Art
For soft magnetic films used as magnetic layers in thin film magnetic heads, planar magnetic elements (e.g., transformers and inductors), or magnetic cores in filters or the like, materials having excellent soft magnetic properties such as resistivity and magnetic permeability, particularly at high frequencies, are required.
An Fe--M(such as Zr, Hf, and Ta)--O system alloy film is considered to be a soft magnetic film having excellent high frequency characteristics. Since this soft magnetic film has high resistivity, eddy current loss can be reduced. The film also exhibits high magnetic permeability at high frequency bands.
However, the Fe--M(such as Zr, Hf and Ta)--O system alloy has a high magnetostriction constant, specifically, of approximately 4.times.10.sup.-6 to 6.times.10.sup.-6.
It is thought that the Fe--M(such as Zr, Hf, and Ta)--O system alloy film includes a fine crystalline phase having a bcc structure containing mainly Fe and an amorphous phase, which surrounds the fine crystalline phase, composed of the oxide of the element M such as Hf. Therefore, presumably it is mainly the fine crystalline phase containing a large amount of Fe that generates magnetism. The reason for an increase in magnetostriction of the soft magnetic film is that Fe which constitutes the fine crystalline phase has large magnetostriction. Additionally, since the fine crystalline phase is not composed of Fe alone and also contains impurities such as Hf and O, the impurities are considered to affect the magnetostriction of the soft magnetic film.
When the Fe--M(such as Zr, Hf, and Ta)--O system alloy having a high magnetostriction constant is used for magnetic layers in thin film magnetic heads or magnetic cores in inductors, soft magnetic properties such as magnetic permeability of the soft magnetic films are easily degraded. Additionally, because of the relationship between internal stress and magnetostriction in the deposited soft magnetic film, the degradation of soft magnetic properties or the separation of the film easily occurs in the soft magnetic film.